Abstract
It is assumed that elevated degrees of fine sediments in river beds affect negatively habitat quality for juvenile Atlantic salmon because of reduction of interstitial space. Finstad et al. [2] developed a simple method to measure interstitial space (shelter availability for salmonids) in running waters. Shelter availability is a candidate mechanism for survival of juvenile salmon due to reduction of predation risk. The goal of this study was to find a relationship between shelter abundance and the associated grain size distribution to be implemented in predictive numerical models for the assessment of the ecological status in running waters. The developed approach was conducted by gathering data in representative places both for shelter abundances and grain size distributions. The results of the study indicate that percentile values generated in grain size analysis are of varying correlation quality related to shelter abundance. Percentiles describing the fine tail of the distribution (D5 and D10) are highly correlated to shelter abundance whereas percentiles describing the middle and coarse part of the distribution (D50, D90) are poorly correlated. Also skewness and geometric mean show relatively high correlation quality. The findings are used to develop assessment and management tools for rivers affected by hydropower regulation.